1. Field
The presently disclosed subject matter relates to a non-spectacled stereoscopic display apparatus.
2. Description of the Related Art
Generally, a stereoscopic display apparatus provides parallax images from viewpoints of both eyes of a viewer. The stereoscopic display apparatus is classified into the spectacled type and the non-spectacled type. The spectacled type stereoscopic display apparatus needs specific glasses, while the non-spectacled type stereoscopic display apparatus needs no specific glasses.
FIG. 17A is a schematic view illustrating a prior art non-spectacled stereoscopic display apparatus, and FIG. 17B is a detailed view of the stereoscopic display apparatus of FIG. 17A (see: JP2010-262198A).
In FIG. 17A, reference numeral 10 designates a non-spectacled stereoscopic display apparatus, and 20 designates a viewer.
In FIG. 17B, the viewer 20 is located in front of a center of a display image of the stereoscopic display apparatus 10.
In FIG. 17B, the stereoscopic display apparatus 10 is constructed by a light guide plate 1 with a light distributing face Sd and a light emitting face Sout1, two light sources 2a and 2b disposed on light incident faces Sina and Sinb of the light guide plate 1, a single-face-deformed triangular prism sheet 3 disposed on the light emitting face Sout1 of the light guide plate 1, a transmissive liquid crystal display panel 4 disposed on a light emitting face Sout3 of the single-face-deformed triangular prism sheet 3, and a synchronous drive circuit 5 for synchronizing the light sources 2a and 2b to display parallax images on the transmissive liquid crystal display panel 4. When one of the light sources 2a and 2b is turned ON, the single-face-deformed triangular prism sheet 3 is configured to emit light to one eye of the viewer with no emission of light to the other eye. Also, provided on the light incident and light emission sides, respectively, of the transmissive liquid crystal display panel 4 are polarizing plates 4a and 4b. Thus, a stereoscopic image with the same number of pixels as that of the transmissive liquid crystal display panel 4 can be displayed.
In FIG. 17B, two light guide plates, i.e., a lower light guide plate and an upper light guide plate superposed onto the lower light guide plate can be provided instead of the light guide plate 1 (see: JP2010-286813A).
In FIG. 17B, when the viewer 20 is moved along the right or left direction as indicated by a dotted line, it is impossible to universally move the location of a stereoscopic image toward the viewer 20.
FIG. 18A is a schematic view illustrating a non-spectacled stereoscopic display apparatus which was already suggested by the inventors of this patent application, and FIG. 18B is a detailed view of the stereoscopic display apparatus of FIG. 18A (see: Japanese Patent Application No. 2010-285192 filed on Dec. 21, 2010, and laid open as Japanese Patent Publication No. JP2012-133128A on Jul. 12, 2012).
In FIG. 18A, the stereoscopic display apparatus 10 of FIG. 17A is replaced by a stereoscopic display apparatus 10′ associated with a sensor 10a for detecting the location of the viewer 20.
In the stereoscopic display apparatus 10′ of FIG. 18B, an optically-modulating structure 7 including a microprism liquid crystal element is added to the elements of the stereoscopic display apparatus 10 of FIG. 17A. As a result, the control circuit 6 receives a signal indicating the location of the viewer 20 to transmit a drive voltage Vd to the optically-modulating structure 7, which will be later explained in detail. For example, when the viewer 20 is moved along the right or left direction as indicated by a dotted line, the control circuit 6 receives the sense signal of the sensor 10a to transmit the drive voltage Vd to the optically-modulating structure 7, so that the location of a stereoscopic image is moved toward the viewer 20.
In the stereoscopic display apparatus 10′ of FIG. 18B, however, since the main polarization direction of the light emitted from the single-face-deformed triangular prism sheet 3 does not always match with the polarizing axis of the optically-modulating structure 7 for moving the stereoscopic image, the optical characteristics would be degraded.
Also, since the location of the transmissive liquid crystal display panel 4 is centered at the display image of the apparatus and the optically-modulating structure 7 changes its optical axis within a few degrees to 20 degrees, the optically-modulating structure 7 needs two distinct modulating structures for the right direction and the left direction, respectively, of motion of the viewer 20, which would require a complex configuration of the optically-modulating structure 7.
Further, since an air gap G1 is present between the light guide plate 1 and the single-face-deformed triangular prism sheet 3, an air gap G2 is present between the single-face-deformed triangular prism sheet 3 and the transmissive liquid crystal display panel 4, and an air gap G3 is present between the transmissive liquid crystal display panel 4 and the optically-modulating structure 7, large differences are generated in refractive indexes among them, which also would degrade the optical characteristics.